Koala populations are declining, and there are needs to reverse this trend. Using social marketing which aims to change behavior for social or environmental benefit, this case study demonstrates how social marketing was applied to achieve environmental change. A pilot program name “Leave It” was designed and developed with dog owners and experts including koala conservation officers and dog trainers in order to reduce dog and koala interactions. A four-week dog obedience training program was implemented, and a mixed method outcome evaluation was undertaken. Results indicate that five of seven dog behaviors measures were changed from baseline to follow-up, namely sit, stay, come back when called every time, wildlife aversion, and stay quiet on command. Findings of this pilot program provide evidence of the effectiveness and potential of social marketing to change behaviors in an environmental context.